# Tagged Questions

The law of conservation of energy, which states that the amount of energy in a system is constant. For questions about Earth's environment, see the climate-science tag instead.

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### Quantum Fluctuations [duplicate]

Energy is converted to mass and mass to energy. But during quantum fluctuations energy is created without mass, does this not violate the law of conservation of mass and energy?
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### Why do many people say that virtual particles do not conserve energy?

I've seen this claim made all over the Internet. It's on Wikipedia. It's in John Baez's FAQ on virtual particles, it's in many popular books. I've even seen it mentioned offhand in academic papers. ...
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### What happens when two bodies collide in a dynamics point of view?

I'm a high school student learning about energy and momentum. What confuses me is the things with elastic and inelastic collisions. I completely (in my opinion) understand those concepts in energy ...
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### How do i find how long an object can coast for?

I am given the mass of an object (a motorcycle), its velocity, the mass of its wheels, and the radius of the wheels. If the object rolls without slipping, how can I possibly find out how high it can ...
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### First law of thermodynamics with additional term

I read in a paper that a "known expression for the heat received by a body" is $$dQ=dU+pdV-\mathbf{v}\cdot d\mathbf{P}$$ where $\mathbf{P}$ is the linear momentum of the body, $p$ is the pressure, $U$...
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### General Definition of Steady State

According to many sources (including Wikipedia, Stephani&Kluge, D.J. Acheson) a steady state ist: In systems theory, a system in a steady state has numerous properties that are unchanging in ...
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### Why do tidal forces not violate conservation of energy? [duplicate]

Europa is an example of a satellite which is heated by tidal forces. The orbit is constant, so how is energy conserved on Europa?
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### Why on a frictionless incline, a rolling object reaches the bottom slower than an non-rolling object?

I am really sure if what my physics teacher told me was correct. But he said, rolling objects has rotational kinetic energy, so not all potential energy they have at the start is converted into ...
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### Do you know the principle which says that connecting two sources of similar kind produces a waste and destruction? [closed]

There is a great article, called commutation cells, which states that you cannot transfer kinetic energy from one container to another immediately, bypassing the potential energy storage. Otherwise, ...
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### How much work can the human body do before dying of exhaustion [closed]

If we could assume: We don't increase our energy from absorbing food. Our human example in scope isn't starving or suffering from malnutrition. I mean how much work can we do until the body would ...
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### I m just try to make Free energy using buoyancy [duplicate]

Can I make power (electricity ) using buoyancy see diagram. if this diagram is possible then how much power i get . I just need formula for upwards speed.
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### Minimum energy required to remove the satellite from its orbit to infinity?

My book says that minimum energy required to remove the satellite from its orbit is equal to its total energy (K.E+P.E). But shouldn't it equal to only the potential energy difference of satellite in ...
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### Energy paradox in fluid mechanics

In a fluid, the specific mechanical energy $$e_{mech}= \frac{P}{\rho} + \frac{v^2}{2} + gz$$. Where $P$ is the static pressure, $\rho$ is the density, $v$ is the velocity, $g$ is the gravitational ...
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### Explain this contradiction of violation of “ energy conservation ” using classical mechanics

Consider a rocket moves upward with some acceleration for a very small time say '$dt$' then the kinetic energy increases (for acceleration). as well as as the potential energy increases (due to height ...
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### When are energy, mechanical energy, momentum, and angular momentum conserved?

I am in AP Physics and my only real hangup is knowing when the said quantities are conserved. Please define what is the SYSTEM in your answer. I kind of have the basic idea. For example, if there ...
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### Given force as function of position, find the total energy as function of time [closed]

Given that the force for a non-linear spring connected to a mass $m$ sitting on a table is $$f(x) = -kx -ax^3,$$ Find the total energy as a function of time $E(t)$. I have no clue where to begin.
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### Is the Hamiltonian conserved or not?

The question is the very last sentence at the end of this post. In this post, I'll first show that the Hamiltonian is conserved since it does not have explicit dependence on time and then show that ...
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### Max extension of spring mass system

While attempting problems of simple harmonic motion I came across this problem, which has gotten me confused. A fixed horizontal spring is stretched by a constant force $F$. I am required to obtain ...
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### Applying conservation of energy to a railgun problem?

When a projectile is lunched due to the Lorentz force($F_L$), how can I apply the conservation of energy that the electrical energy inputted to generate the Lorentz force & magnetic field equals ...
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### How does the tension force of a massless string affect the speed of a mass on its end?

i,j, and k are the unit vectors in the following question, and $\omega$ is the angular velocity. Lets say you have a mass m attached to a mass-less string of length $L$ tied to a peg with no friction....
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### Non-linear pendulum (Whittaker's treatise on analytical dynamics of particles)

Reading through Whittaker's "treatise on the analytical dynamics of particles and rigid bodies" I have a question regarding his analysis of the simple nonlinear pendulum at chapter IV. At some point ...
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### energy conservation in an electric circuit

Define a reactive (lossless) and reciprocal two-port by its impedance matrix $[Z]$, so that $[Z]+[\bar Z] = [0]$ and let the source impedance and open circuit source voltage be $Z_s$ and $V_s$ at ...
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### Where does the energy go in a rocket when no work is done?

While playing Kerbal Space Program, I wondered where my chemical energy would go when fired at 90° to the motion. It would do no work on the rocket, but all that energy has to go somewhere, right? ...
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### Simple harmonic motion, maximum kinetic energy [closed]

Why kinetic energy is maximum at mean position?
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### Heat, Work and Internal energy in closed systems

This has been troubling me for a while now. I know that the performed work equals $P\Delta V$ for isobaric systems and I know that in isochoric systems no work is done, but how do I find the heat $Q$? ...
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### Work done by gravitational force!

Suppose a ball is $10m$ high from the ground. It will have $E_p = 10mg$. Now, if the ball falls freely then we know $E_k$ will be $0.5mv^2 = E_p$. But it is said that the work done by a force will ...